Abstract
Activation of immune cells relies on a dynamic actin cytoskeleton. Despite detailed knowledge of molecular actin assembly, the exact processes governing actin organization during activation remain elusive. Using advanced microscopy, we here show that Rat Basophilic Leukemia (RBL) cells, a model mast cell line, employ an orchestrated series of reorganization events within the cortical actin network during activation. In response to IgE antigen-stimulation of FCε receptors (FCεR) at the RBL cell surface, we observed symmetry breaking of the F-actin network and subsequent rapid disassembly of the actin cortex. This was followed by a reassembly process that may be driven by the coordinated transformation of distinct nanoscale F-actin architectures, reminiscent of self-organizing actin patterns. Actin patterns co-localized with zones of Arp2/3 nucleation, while network reassembly was accompanied by myosin-II activity. Strikingly, cortical actin disassembly coincided with zones of granule secretion, suggesting that cytoskeletal actin patterns contribute to orchestrate RBL cell activation.
Highlights
Activation of immune cells relies on a dynamic actin cytoskeleton
We explored the potential relationship between F-actin wave-like propagation and centripetal reorganization of FCε receptors (FCεR) clusters at the Rat Basophilic Leukemia (RBL) cell interface during activation by fluorescently labeling filamentous actin (Factin) (Lifeact-citrine) and the FCεR clusters (SNAP-Tag and membrane-permeable TMR dye-ligand)
Using advanced optical microscopy in live RBL cells, we demonstrated how cytoskeletal actin patterns characterize RBL
Summary
Activation of immune cells relies on a dynamic actin cytoskeleton. Despite detailed knowledge of molecular actin assembly, the exact processes governing actin organization during activation remain elusive. During network disassembly and reassembly, the patterns seemingly followed the propagation direction of the F-actin wave-like structure (35 of 35 spreading cells; Fig. 1b, c).
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